State three ways in which cell A (vessel) is suited for its functions.

No cell contents so it is hollow allowing water flow. End cell walls have broken down forming a continuous tube giving wider passage. Ligin (in cell walls) gives rigidity giving some mechanical strength.

4 of 10

Cells A (guard cells) possess chloroplasts but cells B (accessory cells of stoma) and C (epidermal cells) do not. Suggest a reason for this difference.

Stomata are randomly distributed.

5 of 10

Outline how phloem tissue is structurally adapted for its role in carbohydrate transport.

End walls of sieve tube elements are perforated. Cytoplasm of sieve tube element has few organelles and no nucleus. Celulose cell walls allow exchange of substances across them.

6 of 10

State the function of the endodermis and root hairs (in roots) and outline how they are structurally adapted for their function.

The endodermis controls the entry of water/salts into xylem and it has a casparian ***** which blocks the apoplast pathway. The root hairs absorb water/salts and it has a large surface area/single cells.

7 of 10

Outline the mass flow hypothesis.

Sugars move from the source (cell) and are actively taken up by phloem companion cells. They are passed to the sieve tubes, where water follows osmotically. This creates a hydrostatic pressure, where sugars are removed from phloem at sink (cell).

8 of 10

What is a xerophyte?

A plant which is adapted to grow in dry conditions/prevent water loss.

9 of 10

Outline the signicicance of sunken stomata.

This creates a chamber of moist air above the stomatal pore which is protected from air currents so transpiration is reduced. This is a xerophytic feature.